Global satellite navigation fulfills pervasive needs. Initially a service for military and general aviation, Global Navigation Satellite Services (GNSS) have expanded into many commercial and consumer products for applications ranging from casual to emergency services. More recently, cellular phones have been developed that provide location based service applications and, in response to government requirements, emergency caller location services. The preponderance of these services is enabled by the US Air Force managed Global Positioning System (GPS). GPS is now or may soon be joined by several additional GNSS systems including: GLONASS (Russia), Galileo (European Space Agency), Quasi-Zenith Satellite System (Japan), the Regional Navigational Satellite System (India), and the BeiDou navigation satellite system (China).
The utility of exact positioning cannot be overestimated when safety and security is involved, and several governments now seek precise location for their respective countries' public communication and first-responder infrastructure. At the same time that they seek this service, their public communication infrastructure is shifting rapidly from fixed circuit switched networks to alternative communication networks such as, for example, Voice Over Internet Protocol (VoIP) networks or other Internet Protocol (IP) networks. However, current IP networks are not geo-referenced to either intelligently route or pinpoint the location of E911 callers or others seeking emergency services or the like. Further, such IP services are generally portable to provide nomadic connectivity.
In this regard, to support the ability to locate IP devices (e.g., including the VoIP-enabled emergency caller), proposals have been offered to provide location information by, for example, manual surveys or mapping of the underlying fixed plant assets, using parasitic methods by acquiring and mapping signals such as WiFi or TV broadcast signals, or new, dedicated signals, using separate spectrum and infrastructure that are deployed for the sole purpose of locating objects, pets, or people. However, these methods may have limited effectiveness, may require service suspension if the user connects at a new location, and may incur additional mapping costs when the user connects at a new location. A common belief or premise of these proposals is GPS cannot operate successfully to reach receiver points located inside buildings and homes due to limits of effective satellite signal sensitivity. This limitation is often attributed to the fact that the satellites are far away and have comparatively limited transmission power. However, given the pervasiveness and existing infrastructure in place with respect to GNSS and especially GPS systems, it is highly desirable to improve the ability for devices to employ GPS in obtaining location information even in the case of difficult environments such as where a receiver is located within a building.